1. Field of the Invention
The present invention relates to a binding apparatus for binding a bundle of blank or printed papers having a regular size, hereinafter referred to as a paper or sheet bundle; a paper or sheet processing apparatus integrated either as a single or separate unit in an image forming apparatus, such as a copy machine, printer, printing press or the like, for applying a predetermined process, for example, sorting, stacking, binding, saddle stitch bookbinding, including a binding process to a paper sheet (recording medium) on which an image is formed by utilizing the above-mentioned binding apparatus and for discharging sheets of paper; and an image forming system comprising the paper processing apparatus and the image forming apparatus.
2. Description of the Prior Art
In recent years, there is an increased requirement of post-treating or post-processing a document which is supplied from an image forming device, such as a copy machine, facsimile, printer or the like. In the staple process, such an increased requirement is also extended to a saddle stitching process in which a paper or sheet bundle is bound at evenly spaced positions (normally at two positions) along the center line of dividing the paper sheet, together with the edge binding process in which the paper bundle is bound along an edge line thereof. In addition, a higher performance for the saddle stitching and folding in a conventional machine having a relatively higher process rate is required even in a machine having a lower process rate, along with an increased requirement for providing such a performance at a reduced cost and for reducing the installation space.
A binding apparatus for performing such a saddle stitching and/or edge binding process has been already disclosed, for instance, in Japanese Patent Publication No. 2703315. In this patent specification, it is shown that a paper binding apparatus comprises a storage section for storing staple needles, a pushing section for pushing out one of the staple needles in each operation and a clinching section for bending the end portion of the staple needle, wherein the clinching section and the staple main body including both the storage section and the pushing section are formed as separate elements, and are separately supported on guide shafts in parallel manner such that they are slidable in a direction perpendicular to the sheet feed direction.
Moreover, in Japanese Patent Laid-Open No. H09-309662, a divided type staple mechanism capable of executing the saddle stitching process has been proposed, wherein paper sheets are bound at several positions by shifting the staple mechanism. In this patent specification, the staple mechanism is equipped with guide shafts aligned in the moving direction of a stapler and support elements (groove molding elements) disposed on the back side receiving a reaction force and in the direction parallel to the guide shafts, thereby enabling both the rigidity and the attitude to be maintained in the binding process.
The invention disclosed in Japanese Patent Publication No. 2703315 deals with a divided type stapler which includes a staple main body and a clinching section respectively as a separate element, whereas the invention disclosed in Japanese Patent Laid-Open No. H09-309662 deals with a divided type stapler which is equipped with guide shafts mounted in the moving direction of the stapler and supporting members disposed on their backside for receiving the reaction force and in the direction parallel to the guide shafts, thereby enabling both the rigidity and the attitude to be maintained in the binding operation.
However, in a structural arrangement of a binding apparatus disclosed in Japanese Patent Laid-Open No. H09-309662, no careful consideration has been given to the following points:
[1] Each of the supporting members is designed in a “U-shaped” element in order to receive the reaction force in the staple operation and to maintain the rigidity thereof. In this case, an increase in the allowable mechanical strength causes the size of the binding apparatus to be increased in the direction of height, thereby making it impossible to miniaturize the structure.
[2] Aside from the supporting members, additional members for receiving a force in the direction opposite to the reaction force of the stapler have to be moved over the entire stroke of movement, thereby enabling a simple structural arrangement not to be attained.
[3] In the structural arrangement, there is a space between the supporting member and a carriage in the stapler, so that an undesired crashing sound is generated between the two elements in the staple operation.
[4] Since the staple binding position is apart from the guide shafts for permitting a parallel movement, the rate of the amount of the shift or deviation of the binding position relative to the amount of inclination of the axis is increased, a possible increase in the mal-binding occurs due to the deviation of the clincher section from the stitcher section.
On the other hand, Japanese Patent Laid-Open No. H10-250909 discloses a binding machine for carrying out the end binding and/or the saddle stitching process, wherein feed rollers capable of being separated from each other and of providing press-contact therebetween are disposed before and after a stapler, and wherein a combination of the action of press-contact and the separation of the feed rollers with the feeding action allows a paper bundle to be fed to the staple position.
Japanese Patent Laid-Open No. 2001-72328 also discloses a binding machine, wherein feed rollers capable of being separated from each other and of providing a press-contact therebetween are disposed before and after a stapler, and wherein a combination of the action of press-contact and the separation of the feed rollers with the feeding action allows a paper bundle to be fed to the staple position, in which case, a folding unit is farther disposed downstream to feed a paper bundle to the folding position.
Furthermore, Japanese Patent Laid-Open No. H11-193162 discloses a method for positioning the saddle stitching and folding areas, wherein an end stopper for adjusting the leading end of the paper sheet is disposed and the paper sheet is moved to the positions of both a staple and folding mechanisms by moving the end stopper forward and backward along a feeding line, and then the saddle stitching and folding are carried out therein.
However, in a binding machine disclosed in Japanese Patent Laid-Open No. H10-250909, a feeding is carried out by two feed rollers, so that the maintenance of the feed quality (accuracy in the feeding and the position of the bundle) (it is difficult to assure the accuracy in the feed timing in the operation of switching between the feed rollers) makes it complicated to control the two feed rollers (timings for the press-contact, separation and feeding). In addition, sensors for detecting the edges of the paper sheet have to be provided in the vicinity of the respective feed rollers, and therefore this causes a complicated structural arrangement along with a complicated process.
Moreover, in the binding machine disclosed in Japanese Patent Laid-Open No. 2001-72328, a paper sheet always passes between the feed rollers before the paper sheet arrives at the folding section, and therefore an application of a mechanical stress onto the paper sheets by the feed rollers provides a possible generation of creases or wrinkles at the binding section. In addition, an increase in the feed line length causes the accuracy of the folding position to be scattered or reduced.
Moreover, in the binding method disclosed in Japanese Patent Laid-Open No. H11-193162, the binding position and the folding position are always determined with reference to the leading end of the paper bundle. It can be stated, therefore, that possible curling, bending and the like of the paper sheets cause the mutual spatial relationship therebetween to be occasionally scattered, thereby making it difficult to maintain a sufficient accuracy. In order to maintain such accuracy, paper press member for adjusting the position between guide plates for the paper sheet is additionally installed. However, this causes to provide a complicated mechanism.
In conjunction with the above, a mount of movement corresponding to the maximum size of the paper sheet in the structural arrangement has to be used in the end stopper. This also provides a disadvantage, i.e., an increased size of the binding machine (an increased length of the feed direction).